The progression of psoriatic arthritis can be a long and frustrating journey. It often begins with a diagnosis of psoriasis – a scaly rash that most commonly develops on the elbows, knees, and scalp, but can occur anywhere on the body. In most patients, that is the extent of their condition. However, in 30% of those with psoriasis, their condition will develop into psoriatic arthritis (PsA). This is characterized by joint pain/inflammation and in some cases, erosion of the nails, or other nail changes. 40% of PsA patients will then go on to develop psoriatic spondylitis (also known as PsA with axial involvement), where the inflammation progresses to the spine, potentially leading to fusion within the vertebrate.
However, beyond spinal involvement, the defining characteristics of psoriatic spondylitis have not been well identified. To evaluate the symptoms of PsA with and without axial involvement, a study was conducted in which researchers analyzed data from the Corrona registry. At the time of the study, the registry contained information from 7,476 patient visits with 2,330 patients from 28 various private/academic practices. Of those patients, 1,530 were reported to have some sort of axial involvement. Upon further analysis only 12.5% of those 1,530 had textbook axial involvement; classified by either a radiograph or MRI showing sacroiliitis or having physician-reported presence of axial involvement.
Demographically, it was found that patients with psoriatic spondylitis tended to be younger and have a history of depression. They also exhibited characteristics of significantly worse overall disease, reflected in their higher BASDAI and BASFI scores, elevated C-Reactive Protein (CRP) levels, higher pain, fatigue, nail psoriasis scores, and higher enthesitis counts. A heavier use of biologics was also found, but this could be due to a number of different factors and the exact cause could not be determined.
Due to the observed negative effects of axial involvement, the existence of inflammation within the spine in PsA patients should be “considered a biomarker of greater overall disease severity and as such, the presence of spondylitis should be looked for in order to treat this aspect of PsA effectively.”
 Corrona registry – One of the largest collections of PsA/SpA patient data that was created to further understand the epidemiology and natural history of Spondyloarthritis conditions including psoriatic arthritis, comorbidities, prescribing practices, and comparative effectiveness.
 Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) – A quick and subjective measure in which patients classify their discomfort level on a scale of 1-10 in 6 different categories, such as fatigue and stiffness, with the numbers then being averaged.
 Bath Ankylosing Spondylitis Functional Index (BASFI) – A quick and subjective test that rates a patient’s confidence in their ability to complete certain activities or tasks, such as putting socks on or standing unsupported for 10 minutes without discomfort.
 C-reactive Protein (CRP) – A blood test that identifies the amount of CRP in a patient’s blood. High levels of CRP indicate high rates of systemic inflammation and is frequent in patients with painful axSpA or AS symptoms.
Sources Used and Further Reading
Axial involvement in PsA linked to greater risk for moderate, severe psoriasis
Corrona Registries: Psoriatic Arthritis and Spondyloarthritis